Need a suggestion for a formal business dinner. Hopefully with an interesting menu.

Hi, I'm hosting a business dinner in Boston on a Monday night in February. It's going to be a pretty formal event, and we'll maybe even book a room (might by 6 people). Would appreciate if the Boston hounds could provide some suggestions that fit the formal requirement, but that also have some "interesting" menu options. Sorry if that's vague, but I'm trying to avoid places that are simply expensive and formal.